The operation of lithographic printing presses involves an interaction of water and ink and the inking system of the lithographic printing process has not changed in any fundamental way since the invention of the offset lithographic press in the early 20th century.
Conventional prior art inking systems employed in offset lithography typically include a series of rollers which deliver ink from an ink source to a rotatable plate cylinder carrying the image to be printed. A dampening unit is utilized in association with the plate cylinder to deliver water to the plate cylinder.
The inking unit of a conventional offset lithography press incorporates different types of rollers. A plurality of form rollers are disposed between and in engagement with a rotating plate cylinder and friction driven thereby. The hard rollers engaging the form rollers are oscillated endways. The surface speeds of the hard rollers, the plate cylinder and the form rollers are the same.
The typical inking unit also includes a second set of hard oscillating rollers in operative association with transfer rollers between the first set of hard oscillating rollers and the second set of hard oscillating rollers to deliver ink from the source of ink to the soft rubber form rollers engaging the plate cylinder. All of the transfer rollers are friction driven and all of the rollers in the inking unit, including the hard oscillating-rollers, the transfer rollers and the form rollers have the same surface speed. The endways oscillation of all of the hard oscillating rollers promotes ink distribution.
Conventional offset lithography presses develop problems when run at high speeds. Inking rollers of such equipment with a 3 inch diameter, for example, rotate up to a speed of 3,500 RPM or 46 feet per second surface speed.
As will be described in greater detail below, one of the problems encountered is misting, that is airborne microscopic balls of ink. Undesirable side effects are ink run off and starvation on the printing form.